Weather Topic: What are Hole Punch Clouds?

A hole punch cloud is an unusual occurrence when a disk-shaped hole appears in a cirrostratus, cirrocumulus, or altocumulus cloud.

When part of the cloud forms ice crystals, water droplets in the surrounding area of the cloud evaporate. The effect of this process produces a
large elliptical gap in the cloud. The hole punch cloud formation is rare, but it is not specific to any geographic area.

Other names which have been used to describe this phenomena include fallstreak hole, skypunch, and cloud hole.

Weather Topic: What are Shelf Clouds?

A shelf cloud is similar to a wall cloud, but forms at the front of a storm cloud, instead of at the rear, where wall clouds form.

A shelf cloud is caused by a series of events set into motion by the advancing storm; first, cool air settles along
the ground where precipitation has just fallen. As the cool air is brought in, the warmer air is displaced, and rises
above it, because it is less dense. When the warmer air reaches the bottom of the storm cloud, it begins to cool again,
and the resulting condensation is a visible shelf cloud.